There are known several methods for producing lower cyclic ketones. For example, according to U.S. Pat. No. 2,223,494, C07C 29/50, 1940, cyclopentanone and cyclobutanone are produced by the oxidation of cyclopentane and cyclobutane, respectively, with air oxygen. The reaction is carried out at 120-170° C., using Co, Mn, Cu, Ce salts as a catalyst. This method is disadvantageous in that a large amount of cyclic alcohol is formed along with the ketone, and in that selectivity drops sharply as the conversion increases.
Cyclopentanone can also be produced by catalytic dehydrogenation of cyclopentanol in the gaseous phase at 250-375° C. over a Cu—Zn catalyst [U.S. Pat. No. 2,377,412, C07C 45/00, 1945] or at 160-250° C. over a Ni catalyst [U.S. Pat. No. 2,371,794, C07C 5/05, 1945]. Practical application of this method involves difficulties in view of the absence of cheap sources of cyclopentanol.
A method is known for producing cyclopentanone from adipic acid [U.S. Pat. No. 5,856,581, C07C 45/48, 1999] or esters thereof [U.S. Pat. No. 4,745,228, C07C 45/48, 1988] in the presence of oxide catalysts. Apart from high cost of the feed stock, the first method is disadvantageous in the necessity of carrying out the process in an aggressive acid medium at a high temperature (200-300° C.). In the case of using esters, an additional step of preparing the latter is required, the process flowsheet becoming thus complicated.
According to U.S. Pat. No. 4,806,692, C07C 45/34, 1989, cyclopentanones can also be produced by the oxidation of cyclopentene in the liquid phase with air oxygen, using a homogeneous catalyst PdCl2—CuCl2 at a temperature of up to 80° C. This method is disadvantageous in a low efficiency of the process and the necessity of using aggressive HCl solution.
In GB Pat. No. 649680, C07C 45/34, 1951 there is claimed a process for the oxidation of olefins into carbonyl compounds with nitrous oxide. According to this process, in particular, it is possible to produce cyclopentanone by oxidizing cyclopentene. This process is disadvantageous in a low efficiency and severe reaction conditions.
A second serious disadvantage of this process is the possibility of flammable mixtures to be formed. In order to rule out explosion hazards, the authors of said GB Patent propose to introduce additionally saturated hydrocarbons into the reaction mixture.
However, as later investigations have shown, mixtures of saturated hydrocarbons with N2O are almost as explosion-hazardous, as mixtures of olefins. Thus, limit concentrations of propylene in N2O are 1.8 to 26.8%, and limit concentrations of propane are 2.1 to 24.8% [G. Panetier, A. Sicard, V Symposium on Combustion, 620 (1995); B. B. Brandt, L. A. Matov, A. I. Rozlovsky, V. S. Khailov, Khim. Prom., 1960, No. 5, pp. 67-73 (in Russian)]. Therefore saturated hydrocarbons, in spite of their smaller reactivity, cannot serve as a means for ruling out explosion hazards.